With regard to the surge protection for electronic circuits, there is known a structure using gaseous discharging, that is, a structure which enables the utilization of a phenomenon that conduction is made when the dielectric breakdown takes place in the gaseous layer in a fine discharging gap arranged between a pair of electrodes causing discharge.
In general, a discharge voltage of gaseous discharging is the function of a product PL of a pressure P of a gas which carries discharge, and a width L of a discharging gap. Therefore, if the discharging gap is wider than a specific width, the discharge voltage rises corresponding to the width of the discharging gap (Paschen's law). Then, in the air of one normal atmosphere, the discharge voltage is minimum when a gap between the electrodes is 7.5 .mu.m. The voltage is approximately 330 V. This voltage is usable for the surge protection of a general electronic circuit. In other words, it is logically possible to implement a surge protection by the provision of a structure in which a discharging gap is arranged in the air layer of a specific width. Actually, however, it is almost impossible to stably maintain an extremely narrow gap of 7.5 .mu.m between the electrodes at all times.
Therefore, in order to use the gaseous discharge for the surge protection, there has been employed a structure which uses a discharge tube. This discharge tube is airtightly formed to make it possible to obtain a practical discharge voltage even in a discharging gap of several hundred .mu.m by filling a discharge gas in it to reduce the minimum breakdown voltage (as disclosed in Japanese Unexamined Patent Publication No. 5-268725 and Japanese Unexamined Patent Publication No. 5-226060, for example). As a result, the structure of a surge absorbing element prepared by use of the discharge tube tends to make the structure complicated, and at the same time, make its size bulky and its configuration inflexible. Further, an element of the kind cannot be of any other types than a single type. Consequently, there is a need for the provision of the element for each of the signal lines which must be protected, hence leading to the need for the circuit device to be made bulky and complicated, and also, to the significant increase of cost. Also, it is necessary to provide a comparatively wide space for installing each of the elements. Particularly, in order to implement the surge protection in the connector stage, the implementation becomes more difficult because of the limited availability of space. There are many more instances that may bring about restricted use of an element of this kind.